1. Field of the Invention
This invention is generally related to devices for sensing uterine contractions during labor, and more particularly, to a system and method for sensing the frequency and duration of contractions, and for estimating the relative intensity thereof.
2. General Background and State of the Art
During a contraction, the muscle tone of the uterus increases. This increase in muscle tone applies pressure to the abdomen. The abdomen hardens and the shape changes due in part to the muscles surrounding the anterior ligament of the uterus pulling the abdomen forward.
It is known to provide systems for estimating the force of uterine contractions during labor, generally known as tocodynamometers, which sense, in relative terms, the increase and decrease in abdominal pressure relating to uterine contractions, and enable evaluation thereof. Such systems have typically included a cantilevered beam as a sensor, and a button as a force collector, which is connected to the sensor by a link pin. The output from the system is sent to a. fetal monitor, which displays the relative pressure in the form of a digital reading and strip chart recording. The clinician, in reviewing the chart recording, can observe the progress of labor in terms of contraction frequency and duration, and can obtain a rough indication of the relative intensity of the contractions.
However, such systems are relatively large and bulky, require relatively large devices to hold them in place, and are expensive. Further, they are relatively difficult to use, require relativly high belt tension which is uncomfortable, and tend to migrate and require repositioning.
It would therefore be desirable to provide a sensing system which would sense the frequency and duration of uterine contractions during labor, and estimate the relative intensity thereof, in a manner which would maximize the sensitivity of the system and enhance ease of use and patient comfort. It would further be desirable to enable unique leveraging thereof, for loading onto the abdomen with the exertion of substantially minimal retention pressure. It would still further be desirable to enable support of the system so as to project into the abdomen wall to efficiently reside below the non-compressed abdominal surface. Moreover, it would be desirable to provide electrical isolation of the patient, to prevent the flow of current thereto
Therefore, there has been identified a continuing need to provide a sensing system which will effectively sense uterine contraction frequency and duration during labor, for enabling efficient estimation of the relative intensity thereof.